1. Field of the Invention
The present invention relates to catheters, and more particularly to a catheter assembly which facilitates the percutaneous drainage of abnormal fluid collections from the human body in an efficient and relatively non-traumatic manner. The invention is applicable to fluid collections located within the thoracic, abdominal, or pelvic cavities, or within organs of the human body.
2. Discussion of the Related Art
A drainage catheter is generally a flexible tube with multiple side openings near the distal end, and is widely recognized as an efficient and effective device for removing fluid collections from the human body. Conventional procedures for placing the drainage catheter inside the human body are time-consuming and require the assistance of other devices including a puncture needle, guide wire, and dilator sheath. The puncture needle consists of an outer cannula having an elongated tube and an inner trocar with a sharpened tip projecting through the distal tip of the cannula.
In use, the puncture needle is first punctured into the human body to reach the fluid collection. The trocar needle is then removed. A specimen of the fluid is obtained by aspiration through the cannula so that the fluid nature of the collection can be confirmed before the actual drainage procedure. This collection is typically obtained before such specimen has been contaminated by an operating instrument.
A guide wire is then positioned to reach the fluid collection through the cannula. Once the guide wire is properly positioned, the cannula is removed. A number of dilator sheaths with tapered distal tip ends, one at a time, are then inserted over the guide wire to dilate the stricture until the size of the drainage catheter is reached. The drainage catheter is then inserted over the guide wire to reach the fluid collection.
Once the drainage catheter is properly positioned, the drainage catheter is fixed externally onto the skin with a fixation device. Abnormal fluid can be removed by suction or drained or siphoned through the drainage catheter into a collection bag.
One disadvantage of this conventional method is that it involves redundant steps of inserting the guide wire and dilator sheaths to dilate the stricture, which can be eliminated by an assembled device specially designed for the drainage of the fluid collections from the human body.
A one-step drainage catheter has been designed to simplify the above procedure. The one-step drainage catheter is a device which includes a trocar preloaded within the catheter. The trocar has a sharp distal tip that protrudes out of the catheter. The trocar and the catheter are locked together at the hub, at the proximal end, so that they function as a unit.
When the one-step drainage catheter is in use, the combined unit of the trocar and catheter is inserted into the collection cavity. The trocar is then disengaged from the catheter and removed. The catheter remains with its distal end positioned for draining the fluid collection.
Although the one-step drainage catheter has greatly simplified the conventional procedure, there are two main disadvantages. First, forceful advancement of the combined unit of the trocar and catheter is required to bring the unit into the human body and to overcome the friction between the body tissue and the catheter tip. The catheter tip is positioned slightly behind the trocar tip, creating an abutment surface on the catheter tip against the body tissue. The abutment surface on the catheter tip is subject to substantial pressure during insertion into the body tissue, which causes great trauma for the patient.
Second, no fluid specimen can be obtained by simply applying the one-step drainage catheter, which is a crucial step to ensure that the catheter tip is properly positioned and the abnormal fluid drained. In some circumstances, the one-step drainage catheter is improperly positioned and no fluid can be drained after insertion. The one-step drainage catheter has to be re-inserted and the patient has to suffer another puncture.
It is also helpful to extract the fluid specimen when the fluid collection is still uncontaminated by any instruments or device. Without the cannula being part of the device, the lumen now being occupied by the trocar, the specimen fluid can only be obtained by a separate needle puncture before the use of the one-step drainage catheter. In that case, the patient will suffer two punctures during the procedure.
U.S. Pat. No. 5,205,830 discloses a catheter assembly comprising a catheter, a cannula, and a dilator. According to the '830 patent, the cannula and dilator are preloaded inside the catheter. An introducer needle (also known as a trocar) is first inserted into the cavity to be drained. A guide wire is then inserted into the introducer needle and the introducer needle is removed. The catheter assembly device is then inserted over the guide wire to reach the fluid collection.
One disadvantage of the '830 patent is that the catheter is inserted into the human body with the cannula, before the specimen fluid can be obtained. Such insertion will encounter more resistance from the body tissue because of the relatively larger diameter of the catheter. If the catheter assembly is not positioned at the desired body cavity location and does not reach the fluid collection, which can be discovered only after insertion of the catheter assembly, the catheter assembly has to be re-inserted and the patient will suffer another puncture. An alternative is to obtain the fluid specimen by a separate needle puncture before insertion of the catheter assembly as described above, but the patient is still forced to suffer two punctures.
Known guide wires are used to guide the insertion of the catheter to reach the drainage system within the organs. A disadvantage is that the guide wire has to be separately held in a relatively stable position during the insertion of the catheter.